This research will investigate the mechanisms by which learning is affected by the context in which it occurs. The focus of the investigation will be operant conditioning procedures where previous analysis of context effects have been ascribed to the molar variable of relative rate of reinforcement. An alternative account, taken from the analysis of parallel context phenomena in Pavlovian conditioning, is that such effects can be understood in terms of the notion of associative competition. This research will investigate whether such an associative approach is applicable to free-operant behavior by determining whether the critical empirical phenomena supporting an associative-competition account in Pavlovian procedures can be demonstrated in free- operant procedures as well. The proposed research will also include an analysis of several major operant phenomena, including the matching law, anticipatory behavioral contrast, and conditioned reinforcement, to determine whether they also are consistent with the notion of associative competition. The results of the research should determine whether a unified explanatory framework is possible for Pavlovian and free-operant procedures, and should provide a deeper understanding of the concept of reinforcement and how its application to applied behavior settings can be utilized most efficiently.